1. Field of Invention
The invention relates generally to the field of data transmission. In one exemplary aspect, the invention relates to the use of a network architecture for providing content and data via content distribution (e.g., cable) networks using a packetized protocol.
2. Description of Related Technology
The provision of content to a plurality of subscribers in a content-based network is well known in the prior art. In a typical configuration, the content is distributed to the subscribers devices over any number of different topologies including for example: (i) Hybrid Fiber Coaxial (HFC) network, which may include e.g., dense wave division multiplexed (DWDM) optical portions, coaxial cable portions, and other types of bearer media; (ii) satellite network (e.g., from an orbital entity to a user's STB via a satellite dish); (iii) optical fiber distribution networks such as e.g., “Fiber to the X” or FTTx (which may include for example FTTH, FTTC, FUN, and FTTB variants thereof); (iv) Hybrid Fiber/copper or “HFCu” networks (e.g., a fiber-optic distribution network, with node or last-mile delivery being over installed POTS/PSTN phone wiring or CAT-5 cabling); (v) microwave/millimeter wave systems; etc.
Various types of content delivery services are utilized in providing content to subscribers. For example, certain content may be provided according to a broadcast schedule (aka “linear” content). Content may also be provided on-demand (such as via video on-demand or VOD, free video on-demand, near video on-demand, etc.). Content may also be provided to users from a recording device located at a user premises (such as via a DVR) or elsewhere (such as via a personal video recorder or network personal video recorder disposed at a network location) or via a “startover” paradigm, which also affords the user increased control over the playback of the content (“non-linear”).
Just as different varieties of content delivery services have evolved over time, several different network architectures have also evolved for deploying these services. These architectures range from fully centralized (e.g., using one or more centralized servers to provide content to all consumers) to fully distributed (e.g., multiple copies of content distributed on servers very close to the customer premises, at the “edge” of the distribution network), as well as various other configurations. Some distribution architectures (e.g., HFC cable, HFCu, etc.) consist of optical fiber towards the “core” of the network, which is in data communication with a different medium (coaxial cable radio frequency, copper POTS/PSTN wiring, etc.) distribution networks towards the edge.
Satellite networks similarly use a radio frequency physical layer (i.e., satellite transceiver and associated settop box and satellite dish located at each of the consumer's premises) to transmit digital television and data signals.
HFCu networks utilize existing copper (e.g., POTS/PSTN or CAT-5) cabling within the premises for the “last mile”; however, one salient downside to this approach is severe bandwidth constraints (e.g., on the order of 25-30 mbps). At 25 mbps, roughly 6 mbps is allocated for Internet access, leaving the remaining 19 mbps for HD/SD video and voice (e.g., VoIP). VoIP bandwidth is effectively trivial for both upstream and downstream bandwidth, but video (especially HD quality) consumes great amounts of bandwidth. Hence, the user of an HFCu system rapidly becomes bandwidth-limited for next-generation/commonly required technologies such as HD video provided with high-speed broadband data service.
While the details of how video is transported in the network can be different for each architecture, many architectures will have a transition point where the video signals are modulated, upconverted to the appropriate RF channel and sent over the coaxial segment(s), copper wiring, (or air interface) of the network. For example, content (e.g., audio, video, etc.) is provided via a plurality of downstream (“in-band”) RF QAM channels over a cable or satellite network. Depending on the topology of the individual plant, the modulation and upconversion may be performed at a node, hub or a headend. In many optical networks, nodes receive optical signals which are then converted to the electrical domain via an optical networking unit (ONU) for compatibility with the end-user's telephony, networking, and other “electrical” systems.
In U.S. cable systems for example, downstream RF channels used for transmission of television programs are 6 MHz wide, and occupy a 6 MHz spectral slot between 54 MHz and 860 MHz. Within a given cable plant, all homes that are electrically connected to the same cable feed running through a neighborhood will receive the same downstream signal. For the purpose of managing services, these homes are aggregated into logical groups typically called service groups. Homes belonging to the same service group receive their services on the same set of in-band RF channels.
Cable and satellite signals are transmitted using a QAM scheme and often use MPEG (e.g., MPEG-2) audio/video compression. Hence, available payload bitrate for typical modulation rates (QAM-256) used on HFC systems is roughly 38 Mbps. A typical rate of 3.75 Mbps is used to send one video program at resolution and quality equivalent to NTSC broadcast signals (so-called “Standard Definition (SD)” television resolution). Use of MPEG-2 and QAM modulation enables carriage of 10 SD sessions on one RF channel (10×3.75=37.5 Mbps<38 Mbps). Since a typical service group consists of 4 RF channels, 40 simultaneous SD sessions can be accommodated within a service group. These numbers work out very well for many deployment scenarios, such as the following example. A typical “service area” neighborhood served by a coaxial cable drop from the cable network consists of 2000 homes, of which about two-thirds are cable subscribers, of which about one-third are digital cable subscribers, of which about 10% peak simultaneous use is expected. Hence, the bandwidth required to meet service requirements is 2000×(⅔)×(⅓)×0.1=approximately 40 peak sessions−the exact number supported by a 4 QAM service group. Since high-definition (HD) sessions require a greater bandwidth (typically 15 Mbps), less of these sessions can be accommodated.
Broadband data carriage in such networks is often accomplished using other (typically dedicated) QAM channels. For instance, the well known DOCSIS specifications provide for high-speed data transport over such RF channels in parallel with the video content transmission on other QAMs carried on the same RF medium (i.e., coaxial cable). A cable modem is used to interface with a network counterpart (CMTS) so as to permit two-way broadband data service between the network and users within a given service group.
Out-of-band (OOB) channels (and associated protocols) may be used to deliver metadata files to a subscriber device, as well as to provide communication between the headend of the content-based network and the subscriber devices.
Other systems and methods may also be used for delivering media content to a plurality of subscribers. For example, so-called “Internet Protocol Television” or “IPTV” is a system through which services are delivered to subscribers using the architecture and networking methods of an Internet Protocol Suite over a packet-switched network infrastructure (such as e.g., the Internet and broadband Internet access networks), instead of being delivered through traditional radio frequency broadcast, satellite signal, or cable television (CATV) formats. These services may include, for example, Live TV, Video On-Demand (VOD), and Interactive TV (iTV). IPTV delivers services (including video, audio, text, graphics, data, and control signals) across an access agnostic, packet switched network that employs the IP protocol. IPTV is managed in a way so as to provide the required level of quality of service (QoS), quality of experience (QoE), security, interactivity, and reliability via intelligent terminals such as PCs, STBs, handhelds, TV, and other terminals. IPTV service is usually delivered over a complex and heavy “walled garden” network, which is carefully engineered to ensure sufficient bandwidth for delivery of vast amounts of multicast video traffic.
IPTV uses standard networking protocols for the delivery of content. This is accomplished by using consumer devices having broadband Internet connections for video streaming. Home networks based on standards such as “next generation” home network technology can be used to deliver IPTV content to subscriber devices in a home.
So-called “Internet TV”, on the other hand, generally refers to transport streams sent over IP networks (normally the Internet) from outside the network (e.g., cable, HFCu, satellite, etc.) that connects to the user's premises. An Internet TV provider has no control over the final delivery, and so broadcasts on a “best effort” basis, notably without QoS requirements.
There is also a growing effort to standardize the use of the 3GPP IP Multimedia System (IMS) as an architecture for supporting IPTV services in carriers networks, in order to provide both voice and IPTV services over the same core infrastructure. IMS-based IPTV may be adapted to be compliant with the IPTV solutions specifications issued by many IPTV standards development organizations (SDOs), such as, e.g., Open IPTV Forum, ETSI-TISPAN, ITU-T, etc.
While delivery of packetized content is well known in the prior art, the ability to provide delivery of packetized (e.g., IP) media content to a subscriber device over a content delivery network (e.g., cable television HFC, HFCu, satellite, etc.), other than over the Internet as afforded by virtue of a satellite, cable, or other such modem (i.e., “Internet TV”), and/or by using expensive spectrum resources (e.g., via a CMTS), has been lacking. Still further, these systems require content to be duplicated for enabling legacy (non-IP enabled) CPE access, thereby requiring duplicate spectrum to be occupied.
Moreover, extant Internet TV and IPTV solutions (regardless of bearer medium) lack the ability to provide the entire “carrier class” (i.e., high quality/bitrate content) stream; i.e., all content which would be available using linear content delivery methods, as well as other content types (e.g., video on-demand (VOD), network digital video recorder (DVR) content, etc.). It is further noted that current carrier class stream delivery mechanisms require mechanisms for conserving and/or efficiently using bandwidth. For example, Broadcast Switched Architecture (BSA; also commonly known as “switched digital video” or “SDV”) content delivery networks, such as that described in co-assigned application Ser. No. 09/956,688, filed Sep. 20, 2001 and entitled “TECHNIQUE FOR EFFECTIVELY PROVIDING PROGRAM MATERIAL IN A CABLE TELEVISION SYSTEM”, incorporated herein by reference in its entirety, may be utilized to selectively deliver only a subset of available programming to network subscribers in order to optimize bandwidth. Delivery of programming under this mechanism is typically based on customer requests (or lack thereof) for programming; however, bandwidth consumption may vary greatly during the day. In a fixed bandwidth model, the BSA architecture delivers a fixed amount of programming based on the fixed bandwidth constraint; the programming actually delivered at any given time will be only a fraction of the total of the programming available to the user base.
One prospective solution to delivering carrier class programming in a packet transport form (e.g., H.264 encoded content in an IP wrapper) is to obtain additional high-capacity CMTS equipment that would enable generation of additional downstream QAMs to carry the content. This CMTS-based approach suffers from several disabilities, however, including: (i) the comparatively high cost and high degree of infrastructure modification required; and (ii) the need to carry both traditional (e.g., MPEG-2) and next generation (e.g., IP encapsulated) content streams in parallel to service legacy and IP STBs, respectively.
A network operator such as a cable MSO must manage and reduce the “cost-per-channel” so as to be competitive with other delivery paradigms such as broadcast switched architecture (BSA) and VOD. Development of highly specialized and high-capacity CMTS equipment to deliver the next generation IP content in sufficient quantity requires very significant NRE (non-recurring engineering) and development costs, and moreover the number of such devices needed within all content delivery networks will be comparatively small, thereby tending to minimize any downward price pressure for this equipment (and hence reducing its cost viability in comparison with BSA, VOD, or other low-cost legacy delivery models).
Additionally, the aforementioned CMTS-based approaches generally segregate the QAM pool used for delivery of the IP services from those used to carry broadcast or linear content. This results in not only the need for more equipment and QAMs, but also necessitates at least to some degree the carriage of both legacy (e.g., MPEG-2) and IP content, since the next-generation IP STBs cannot decode the MPEG-2 streams, and vice versa. This is obviously very bandwidth inefficient.
For example, one such prior art approach is offered by BigBand Networks, Inc., and effectively segregates IP-carrying QAMs into a pool viewable only by IP-enabled STBs. However, the IP encapsulation is performed at the network headend, and no free intermixing of the IP-carrying streams and normal broadcast content occurs.
Hence, improved apparatus and methods are needed to provide delivery of the entire carrier class stream as IP packetized content to consumer devices, while still maintaining delivery of this carrier class stream in the form of legacy linear (e.g., MPEG-2 broadcast) content, and without any significant modification of the network infrastructure, or additional investment in spectrum. Ideally, the two types of content (legacy and next-generation IP content) could be freely intermixed on extant network infrastructure, even at the service group level so as to allow legacy and IP-enabled users within a service group to be serviced by the same infrastructure, and in a cost-efficient manner.